Chris will feature on one of Ri-Ri's songs

Rihanna is working with ex-boyfriend Chris Brown on a remix of her song Birthday Cake.

Chris, 22, has reportedly recorded both a singing and rap verse which he hopes will make the final cut on the mash-up of the track from Rihanna‘s latest album Talk That Talk.

‘The feature on this remix is gonna shock the world,’ say the song’s co-producers Da Internz.

It seems as though Ri-Ri, who turns 24 today, has forgiven Chris for violently assaulting her in 2009.

She invited him to her pre-birthday party at a Beverly Hills mansion last week and this morning Chris sent a Happy Birthday message to his Brits-nominated ex using her real name, Robyn.

HAPPY BIRTHDAY ROBYN!’ Tweets Chris.

‘Thanks! RT @chrisbrown: HAPPY BIRTHDAY ROBYN!’ replies Rihanna.

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Anna Duff